Electron discharge tube



Jan. 12, 1937. F, HEHLGANS 2,067,840

A ELECTRON DISCHARGE TUBE Filed Nov. 28, 1932 l if f lrwverwtcr: Friedr ch Heh! ans,

H is Attovrwe.

Patented Jan. 12, 1937 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE TUBE poration of New York Application November 28, 1932, Serial No. 644,718

4 Claims.

The present invention relates to electron discharge tubes, particularly to cathode-ray tubes employed for sound film purposes. In tubes of this character, it is customary to use a cylinder for controlling the intensity of the cathode-rays .and this cylinder has usually been positioned between the anode and cathode of the tube. While the cylinder has offered a certain amount of control to the electron stream, it has been found that the voltages required for control purposes are comparatively high.

An object of the present invention is to improve tube structures of this sort to the end that the control voltages may be materially reduced without sacrifice of control eiciency. In carrying out this object, and in accordance with the present invention, the control cylinder is moved from its usual position, to a position between the anode and the uorescent screen on which the electrons impinge. It has been found that this change in position effects the same degree of current control but with much smaller control voltages than are required in prior arrangements, consequently, the amount of amplication necessary for sound film recording is materially decreased. The invention will be more fully understood when reference is made to the drawing which shows a longitudinal cross-section of a tube improved in accordance with the invention.

In the drawing, numeral I designates the envelope of a highly evacuated or gas-filled tube. The gas filling may comprise argon or mercury vapor at the usual pressures. The envelope contains the cathode 2 which is illustratively exemplied as being indirectly heated, a focusing cylinder 3 surrounding the cathode and an anode 4 which may constitute a metal plate provided with a central opening 5 in line with the focusing cylinder and cathode. The electrodes are supported from the reentrant stem 6 in any suitable manner, for example, by means of rigid leading-in conductors and if desired, a glass pant-leg 'l may be provided around the anode leading-in conductor to prevent undesirable secondary emission.

In accordance with the present invention, there is provided a hollow metal cylinder 9 which is suitably positioned between the anode 4 and the fluorescent screen l0 coated on the envelope. The screen is electrically independent of all of the electrodes, including the anode and assumes its own potential. The cylinder 9 is conveniently supported from the stem 6 by Germany December 5, 1931 (ol. 25o- 2715) means of a rigid leading-in conductor covered, if desired, by a glass pant-leg Il. The cylinder 9 is preferably positioned in line with the opening in the anode.

The improved tube may be used for sound lm purposes or for sound recording in the ordinary manner, for example, by projecting the iiuorescent spot appearing on the screen lll, as a narrow light strip on a lm which passes in front of the fluorescent screen. If desired, electrostatic deflecting plates may be introduced into the tube in addition to the current intensity control cylinder. The condensation of the light into a narrow strip may be obtained in any suitable manner, for example by the usual diaphragm arrangement or by an optical system. The intensity or brightness of the fluorescent spot is varied by controlling the voltage applied to the cylinder 9.

Demonstrations have shown that the intensity of the electron beam can be satisfactorily controlled by a control voltage i-'I volts by the improved position of the control cylinder with an anode voltage of approximately 800 volts, and a voltage at the control cylinder 9 of 15 volts negative with respect to the cathode, i. e., relatively small potential with respect to the cathode. In the prior art arrangement where the control cylinder is positioned between the cathode and the anode, a control cylinder voltage of volts and a control voltage of x45 volts is required for the same degree of control, when the anode voltage is of the order of 800 volts.

The dimensions of the electrodes should of course be determined by calculation and operation but typical dimensions are as follows: Diameter of the metal cylinders 9 and 3, approximately 8 millimeters; length approximately 6 millimeters; distance from the anode 4 approximately 5 millimeters; diameter of the plate-like anode approximately 16 millimeters; and the diameter of the opening 5 in the anode, approximately 2 millimeters.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. In combination an electron discharge device comprising an envelope containing an electronemitting cathode, an anode having an opening through which the electron stream passes, a uorescent screen on which the electrons impinge, and means positioned between the anode and screen for electrostatically controlling the intensity of the stream as it passes between the anode and screen, and means for applying variable potentials to said control means.

2. In combination an electron discharge device comprising an envelope containing an electronemittng cathode, an anode having an opening through which the electron stream passes, a fluorescent screen onWhich the electrons impinge, and means positioned between the anode and screen for electrostatically controlling the intensity of the stream as it passes between the anode and screen, said means including a metal member adapted to receive Variablegpotentials, and means for biasing said metal member and applying variable potentialsthereto.'

3. In combination an electron' discharge device comprising an envelope containing an electron-emitting cathode, an,4 anode having' an opening through which the electron 'stream` passes, a fluorescent screen electrically independent of the anode, and means positioned between the anode and screen for electrostatically controlling the intensity of the stream as it emerges from the anode opening and impinges on the screen, and means for applying Variable potentials to said control means.

4. An electron discharge tube comprising an envelope containing an electron-emitting cathode, a focusing cylinder surrounding said cathode, an anode, a fluorescent screen electrically independent of the anode, and a hollow metal cylinder adapted to receive charges of variable potential and positioned between the anode and screen, in line with the electron stream for controlling the intensity of the current passing between the anode and the screen.

FRIEDRICH HEHLGANS. 

